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Chem 110 > Block 6: Functional Groups II > Flashcards

Block 6: Functional Groups II Flashcards

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1
Q

How does ethanol act as a base?

A

CH3CH2OH + Na+NH2- –> CH3CH2O-Na+ + NH3

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2
Q

How does ethanol act as an acid?

A

CH3CH2OH + H2SO4 —> CH3CH2OH2 + HSO4-

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3
Q

What is the conjugate base of an alcohol called?

A

An alkoxide ion

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4
Q

What is the conjugate acid of an alcohol called?

A

An oxonium ion

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5
Q

Why are the alkoxide and oxonium ions important?

A

They act as EXCELLENT nucleophiles and electrophiles in the synthesis of organic compounds

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6
Q

Are phenols acidic or basic?

A

Phenols are vaguely acidic as their conjugate base in an electron donating group, causing the ring to become resonance stabilized.

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7
Q

How do electron withdrawing groups affect the acidity of a phenol?

A

They make it more acidic as they stabilize the phenoxide anion further

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8
Q

How do electron donating groups affect the acidity of a phenol?

A

They make it less acidic as they destabilze the phenoxide anion

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9
Q

How do you know whether an alcohol will react via Sn1 or Sn2?

A

Same rule as for haloalkanes

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10
Q

How can alcohols be prepared?

A 
Alkyl Halide Hydrolysis
Acid catalysed addition of H2O
Hydroboration-oxidation
Reduction of aldehyde/ketone/ester
Grignard reagents with Methanal, other aldehydes, ketone, esters or acyl chlorides.
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11
Q

What is the mechanism of an alcohol being formed via alkyl halide hydrolysis?

A

CH3Br + OH- –> CH3OH + Br- (Sn2)

(CH3)3CCl +H2O –> (CH3)3C+ +Cl –H2O–> (CH3)3CO+H2 — -H –> (CH3)3COH + HCl

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12
Q

What is the mechanism of an alcohol being formed via acid catalysed addition of H2O?

A

CH3CH=CH2 + H2O —(H+) –> CH3CH(OH)CH3 + CH3CH2CH2OH

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13
Q

What reagent do you use if you want the minor product of an addition reaction with alcohol?

A

B2H6/OH-

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14
Q

What is the mechanism of an alcohol being formed via hydroboration oxidation?

A

CH3CH=CH2 —(B2H6/H+)–> CH3CH2CH2BrH2 —> CH3CH2CH2OH

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15
Q

What does an aldehyde reduce to?

A

Primary aclohol

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16
Q

What does a ketone reduce to?

A

Secondary alcohol

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17
Q

What does an ester reduce to?

A

2x primary aclohols

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18
Q

What are the reagents you could use to reduce an aldehyde/ketone/ester?

A

LiAlH4 or NaBH4 with H3O+

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19
Q

What is formed when methanal reacts with a grignard reagent?

A

Primary alcohol with an extra carbon

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20
Q

What is formed when an aldehyde other than methanal reacts with a grignard reagent?

A

Secondary aclohol

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21
Q

What is formed when a ketone reacts with a grignard reagent?

A

Tertiary alcohol

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22
Q

What is formed when an ester or acid chloride reacts with a grignard reactant?

A

A tertiary alcohol is formed with 2 identical R groups.

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23
Q

What are the ways in which new C bonds can be formed?

A

Grignard reagents, nitriles, and alkynides (Grignard most likely)

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24
Q

What are the reactions an alcohol can perform?

A

Substitution
Elimination
Oxidation

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25
Q

What reagents are needed for an alcohol to form a haloalkane?

A

Addition of SOCl2 (if primary or secondary) or HCl (if tertiary)

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26
Q

What is the mechanism of Sn1 and Sn2 alcohol substitution?

A

CH3OH –(SOCl2) –> CH3Cl

(CH3)3COH + HCl –> (CH3)3CCl + H2O

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27
Q

What reagents are needed for an alkoxide to form an ether?

A

CH3CH2O- + RX –> CH3CH2COR + X-

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28
Q

What reagent is needed to form an alkene from an alcohol?

A

Concentrated H2SO4 and Heat.

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29
Q

Why does the alcohol have to be protonated (unlike the haloalkane) to form an alkene?

A

Because OH on its own is a poor leaving group, but H2O is very good.

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30
Q

What is the mechanism of a tertiary alcohol becoming an alkene?

A

CH3CH2OH —>H3O+/Heat—> CH3CH2OH2+ —> CH3 CH2+ +H2O —-> CH2=CH2

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31
Q

What is the mechanism of a 1/2 alcohol becoming an alkene?

A

CH3CH2OH + H2O—> transition state with a bond breaking between H anc C and C and OH2+, with a bond forming between H and OH and C and C

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32
Q

What do primary alcohols form when they are oxidised with H2CrO4?

A

Carboxylic acids

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33
Q

What to primary alcohols form when they are oxidised with PCC?

A

Aldehydes

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34
Q

What do secondary alcohols form when they are oxidised with H2CrO4?

A

Ketones

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35
Q

How are ketones formed on a ring structure?

A

Acid chloride + AlCl3 —> Ph-COCH3 + HCl

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36
Q

How do A/K undergo nucleophilic addition? (general)

A

RCOR + Nu- —> RC(O-)NuR — (H+) —> RC(OH)NuR (Only works with strong nucleophile)

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37
Q

What is a second way for A/K to undergo nucleophilic substitution?

A

RCOR + H+ —> RCOHR +Nu-H —-> RC(OH)Nu-H)R — (-H+) –> RC(OH)NuR

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38
Q

What does the oxonium ion method of a/k substitution require?

A

A weak nucleophile with an Nu-H bond.

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39
Q

How does the rate of reaction for a/k nucleophilic substitution change depending on the carbonyl’s R groups?

A

2Hs = fast
1H 1Alkyl/aryl = between
2alkyl/aryl = slow

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40
Q

Why does the trend in reaction rate for a/k substitution exist?

A

This is due to the electronic and steric effect changing the size of the delta +/- charges.

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41
Q

What is the reagent needed for an a/k to react with cyanide?

A

-CN/H3O+

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42
Q

What is the mechanism for an a/k reaction with -CN?

A

RCOR + -CN –> RCO(-)CNR –> RC(OH)CNR —-(H3O+) RC(OH)COOHR

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43
Q

What are possible oxygen nucleophiles that can be added to an a/k?

A

H2O, ROH

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44
Q

What is the reaction of an a/k reacting with water?

A

RCOR + H2O –> RC(OH2)R

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45
Q

What should be remembered about an a/k reaction with water?

A

Alkehydes favor the products more than ketones due to H2O being a good leaving group

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46
Q

What is the mechanism of an a/k reaction with an alcohol?

A
  1. RCOR + H+ —>RCOHR + ROH –> RC(OH)(OHR+)R — (-H) RC(OH)(OR)R (Called a hemiacetal)
  2. RC(OH)(OR)R + ROH —> RC(OR)2R +H2O (called an acetal)
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47
Q

Why are acetals important?

A

They serve as ‘protecting groups’ in the synthesis of some molecules

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48
Q

What are some nitrogen nucleophiles which a/ks could react with?

A

RNH2
NH2OH
H2NNH2

49
Q

What is the mechanism for an a/k reaction with a nitrogen nucleophile?

A

RCOR + R’NH2 RC(OH)(NH2R’+)R —(-H2O)–> R(C=NR’)R

50
Q

What is RC(NR)R called?

A

An imine

51
Q

What is RC(NOH)R called?

A

An oxime

52
Q

What is RC(NH2)R called?

A

A hydrazone

53
Q

How do you remember what reagent to use when forming a compound using a nitrogen reagent?

A

It’s always (whatever you want) attached to an NH2 group.

54
Q

What is an alpha carbon?

A

A carbonyl carbon

55
Q

What is the requirement for a carbonyl to form an enol or enolate?

A

It must have an H on a vicinal C to the alpha carbon

56
Q

How does a carbonyl carbon form an enol?

A

CH-C=O + HB —> (Sn2 transition state) C=COH + HB

57
Q

How does a carbonyl carbon form an enolate?

A

CH-C=O + B- —> C=CO- + HB

58
Q

Which is more useful out of an enol and enolate?

A

Enolate as it’s negatively charged and so way more reactive and useful for synthesis.

59
Q

How is the enolate anion stabilised?

A

It can delocalise its charge to the vicinal Carbon

60
Q

Why is an enol difficult to isolate?

A

It exists almost entirely in its ketone form (more stable)

61
Q

Why do enols spend almost all their time in keto form?

A

The C=O bond is stronger than the C=C bond, making it more stable

62
Q

What does tautomerisation mean for the isolation of an enolate anion?

A

A strong base is needed (OH-, RO-, NH2- or H-)

63
Q

What can enols and enolates be used for?

A

Alkylation reactions- joining of an R group.

64
Q

How does alkylation proceed when acid catalysed?

A

An RX + the enol causes the R to join to the double bond, and the O double bond to reform. This causes the R group to join the alpha carbon and a carbonyl carbon, with expulsion of HX.

65
Q

How does alkylation proceed when base catalysed?

A

An RX + an enolate cause the R to join the double bond, and the O double bond to reform. This causes the R to join the alpha carbon and a carbonyl carbon, with expulsion of X-.

66
Q

Which is better and why- acid or base catalysed alkylation?

A

Base catalysed as the enolate is more reactive than the enol.

67
Q

How does an aldol form?

A

A base removes the alpha hydrogen from a carbonyl compound, forming a carbanion. Following this, a second carbonyl reacts with the anion, and the negative carbanion carbon joins to the delta positive carbonyl carbon, forming a bigger structure. The negatively charged ex-carbonyl Oxygen then re-takes the hydrogen, forming an alcohol on one side joined to an aldehyde on the other- an aldol.

68
Q

How does an aldol form an enal?

A

If the alcohol group neighbours a Carbon with a Hydrogen, these can react to come off, forming a double bond in their place- giving the final product as an enal.

69
Q

What needs to be remembered about substituents on Carboxylic acids?

A

With substituents joined directly to acids in straight chained molecules, or ortho/para in aromatic acids, the acid’s pKa is affected by whether the substituent is withdrawing or donating. If the directly attached atom of the substituent has a delta + charge it withdraws electrons, and those with lone pairs of electrons donate electrons.

70
Q

Do electron donating groups increase or decrease acid strength?

A

They decrease the acid strength as larger alkyl groups push more electrons into an already negatively charged compound, destabilizing the ion and making it less likely to form.

71
Q

Do electron withdrawing groups increase or decrease acid strength?

A

They increase acid strength as they have a slight delta plus charge, allowing them to absorb the negative charge and make a more stable resonance structure, making the ion more likely to form.

72
Q

Do halogens on the alkyl substituent increase or decrease the acid strength?

A

Increase as they are highly electronegative, making the attached C even more positive and able to accept an electron.

73
Q

Are acids or phenols more soluble in Hydrogencarbonate (acid) and why?

A

Acids are more soluble as the conjugate acid which is formed is weaker than the acid itself, so is more product favored. However, the phenol is a weaker acid than the potential conjugate, and so is not as soluble as the reaction is reactant favored.

74
Q

What are the ways of preparing a carboxylic acid?

A

Oxidation of a primary alcohol/aldehyde
From a grignard reagent with CO2
From a nirile

75
Q

How do you prepare a carboxylic acid from a grignard reagent and CO2?

A

R-MgX + CO2 —> R-C=O(OMgX) –(H3O+)–> RCOOH

76
Q

How do you make carboxylic acid from a nitrile?

A

R-X + -CN –> RCN + Br- –(H3O+)–> RCOOH + NH3

77
Q

What are the derivatives of carboxylic acids?

A

Acid chlorides, Carboxylic acids, Acid Anhydrides, Esters and Amides

78
Q

What is the process of substituting a carboxylic acid derivative?

A

RCOY + Nu- –> RC(Nu)(O-)Y –> RCONu + Y-

79
Q

What is the reactivity order of carboxylic acid derivatives?

A

Acid Chlorides > Acid Anhydrides > Esters > Amides

80
Q

What step is the slow step of the substitution of carboxylic acid derivatives?

A

The joining of the nucleophile

81
Q

Why is the reactivity order the way it is?

A

As the breaking of the C-Y bond is the slow step, the reactivity has nothing to do with the leaving ability of Y. If the Y group is electron withdrawing, the C will be more positive, allowing it to be attacked more effectively by the nucleophile. However, if the group is electron donating it makes the C less positive, making it less reactive with a nucleophile.

82
Q

How do you prepare an acid chloride?

A

RCOOH + SOCl2 –> RCOCl + HCl + H2O

83
Q

What can acid chlorides form?

A

Acids (H2O), Amides (NH2R), Esters (ROH) and Anhydrides (RCOOH)

84
Q

How do acid chlorides react with grignard reagents?

A

RCOCl —(2R’MGX/H3O+)—>RC(R’)2OH

85
Q

What is an acid anhydride?

A

R-C=OOC=O-R

86
Q

How is an acid anhydride formed?

A
  • 2x Carboxylic acids with P2O5 form acid anhydride symmetrically with H2O
  • Acid chloride with a carboxylate ion to form unsymmetrical acid anhydride and Hydrogen Chloride
87
Q

How can acid anhydrides react?

A

Form an ester with an alcohol, amide with NH2R and a carboxylic acid with H2O

88
Q

How is an ester formed?

A

Acid chloride + alcohol/phenol
Carboxylic acid + Alcohol
Acid anhydride + alcohol

89
Q

How do esters react?

A

They are slower than acid chlorides or anhydrides.
They form amides with RNH2 and carboxylic acids with H2O in either acidic or basic conditions (to form a carboxylic acid and alcohol)
They can also be reduced to produce two primary alcohols, (the carbonyl side is always primary)
Finally, grignard reagents form a tertiary alcohol with two equivalent groups (using two equivalents of ester).

90
Q

What biological application do esters have?

A

Polyesters are used to form stitches, which are broken down by the slight acidity of body fluids- thus forming dissolvable stitches.

91
Q

How do you make amides?

A

From an acid anhydride, ester or acid chloride with RNH2

92
Q

How do amides react?

A

They form RNH3+ and a carboxylate anion with H3O+ and heat, and further reaction of the RNH3+ with OH- forms RNH2
With H2O to form Acids

93
Q

How do polypeptides form?

A

diacid chlorides and diamides form a peptide bond

94
Q

Why are amides neutral, rather than basic?

A

The resonance from the double bond on O to the N reduces the availability of the electron pairs.

95
Q

What are the seven types of reactions?

A 
Electrophilic Addition
Nucleophilic Addition
Nucleophilic Substitution
Nucleophilic Acyl Substitution
Elimination
Oxidation
Electrophilic Aromatic Substitution
96
Q

What are the three combinations of reactions?

A

Nucleophilic Addition with Nucleophilic Substitution
Nucleophilic Addition with Elimination
Nucleophilic Acyl Substitution with Nucleophilic Addition

97
Q

What are some examples of electrophilic addition?

A

Alkene + H2/Pd OR X2 OR HX OR H2O/H2SO4

Alkyne + Lindlar Catalyst OR Li/NH3/H3O+ OR H2/Pd OR X2 OR HX OR H2O/H2SO4

98
Q

What are some examples of Nucleophilic addition?

A

C=O + NaBH4/H3O+ OR ROH/H+ OR CN-/H3O+ OR RMgX/H3O+

99
Q

What are some examples of Nucleophilic substitution?

A

COH + HCl

CX + OH- OR CN- OR C=_CR- OR OR-

100
Q

What are some examples of Nucleophilic Acyl substitution?

A

C=OR + SOCl2 OR NH2R OR RCOOH OR ROH

101
Q

What are some examples of elimination?

A

CHCX + OH-
CHCOH + H2SO4 conc
CXHCXH + OH-

102
Q

What are some examples of Oxidation?

A

Alcohol –> Ketone/aldehyde/carb. acid

103
Q

What are some examples of Nucleophilic addition + substitution?

A

Aldehyde/ketone to hemiacetal & acetal using (2)ROH/H+

104
Q

What are some examples of nucleophilic addition + elimination?

A

Aldehyde/ketone to imine, hydrazone and oxine

105
Q

What are some examples of Nucleophilic acyl substitution with nucleophilic addition?

A

Ester with LiAlH4 and H3O+ to form primary alcohols

Ester/Acid chloride with 2RMgX?H3O+ to form a tertiary alcohol with two identical R groups

106
Q

How are amines classed?

A

Primary, secondary or tertiary based on how many Cs there are bonded to the N

107
Q

What are aromatic amines?

A

NR2 groups bonded directly to the benzene ring

108
Q

Why are amines good nucleophiles or bases?

A

They have a lone pair of electrons on the N, and so are able to accept a proton

109
Q

What can be used to determine the basicity of an amine?

A

The higher the pKa (weaker acid) the conjugate acid is, the stronger the basicity of the amine

110
Q

What determines which class of amine is more basic and why? What is the trend?

A

Generally, the more R substituents on an amine, the more basic it is as the extra electron density on the N makes it more negative. However, a tertiary amine doesn’t follow this pattern as the increased R groups make the compound more crowded, preventing it from gaining a proton as efficiently.

111
Q

Why are aromatic amines much weaker than alkylamines?

A

The lone pair of electrons on N is donated into the ring, causing it to become resonance stabilized and less likely to react

112
Q

What effect do electron withdrawing and donating groups have on an arylamine’s basicity?

A

Electron withdrawing groups decrease basicity as they further stabilize the lone pair of electrons, making them less able to react as a base
Electron donating groups increase basicity as they add to the already negative charge, making it more concentrated and allowing N to act as a base

113
Q

How are alkylamines prepared, but what is the issue with this?

A

They are prepared by substituting haloalkanes with NHR2 groups. However, each product is more reactive than the reactants, so you get a the produced CH3CH2NH2 reacing with the CH3CH2Br used to produce it. This results in a secondary amine, then tertiary, and eventually a quarternary ammonium salt. It is therefore not a good way of isolating amines, as a mixture results

114
Q

How do arylamines form by subtitution?

A

By reacting Ph-NO2 with Fe/H+ and OH-, and NH2 group is substituted onto the ring, or an NHR or NR2 groups, if a 2ry or 3ry amine is requried.

115
Q

How do amines form from reduction?

A

Reduction of a nitrile, primary amide, primary imine or oxime with LiAlH4/H3O+ results in a primary amine
Reduction of a secondary amide or an N-substituted imine results in a secondary alcohol
Reduction of a tertiary amide results in a tertiary bond
NB: The C with the original multiple bond always becomes a CH2 group!

116
Q

How do amines react with halogens/acyl chlorides?

A

The reactions with haloalkanes are unstable, as mentioned in another card
Primary amines reacting with acyl chlorides form a secondary amide, while secondary amines form tertiary amides.
Tertiary amines cannot react with acid chlorides as they don’t have a removable H.

117
Q

How do primary arylamines react?

A

They form diazonium ions in the presence of HNO2 at 0 degrees celsius

118
Q

Why are diazonium ions important?

A

They are intermediates in promoting the formation of meta substituted products, as they are meta directors which can be substituted after direction to form an o/p director. This allows the formation of a benzene ring with two o/p directors meta to one another

Chem 110 (6 decks)

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